Pills and Potions
by KingPreussen
Summary: The Matsuno sextuplets participate in a test. - Temporary Age Regression, PWP, Humor, Mild Language


**direct crosspost from AO3**

i wrote this for a friend in the fandom a while ago

* * *

Jyushimatsu was always bringing home pills and potions from Dr. Dekapan's place.

It would have been one thing if he were lifting them with sticky fingers just to see what they did for himself. It was another that Dekapan told him exactly what everything did and insisted he take them home to share with his brothers. One of them might resent being experimented on if they stopped to think about it, but that wasn't the Matsuno way.

"He said they change your size based on your mood!" Jyushimatsu said with a serious expression, holding the small bottle of orange pills up in the middle of the living room and peering into it. "He said, if you feel small, it will make you small! And he said, if you feel big, it will make you big!"

Osomatsu rubbed under his nose and rolled onto his back. "What if you want just your dick to get big?" Choromatsu kicked at him and he snickered into his comic.

"Kusomatsu would end up 100 meters tall," Ichimatsu muttered under his breath. Which he knew wasn't quite true-they would all end up around a few centimeters taller or shorter and that's it-but Karamatsu looked at him briefly over his mirror and Ichimatsu could see his smile in his eyes.

"Are you gonna take any, Osomatsu-nii-san?" Todomatsu asked.

Osomatsu rested his comic book on his chest and twisted his lips in thought. "Nose goes!" he shouted suddenly, and everyone's hands flew to their faces. Everyone except Karamatsu.

"Oooh, Karamatsu-nii-san!" Jyushimatsu said, bouncing on the balls of his feet with his normal otherworldly grin. "You have to take one! House rules!"

Karamatsu set his mirror down very gently. "Alright, Jyushimatsu. I'll take it. But only if Osomatsu goes first next time."

Everyone except Osomatsu agreed readily, overpowering the eldest's incensed "hey!", and Karamatsu held out his hand for a pill. Even Choromatsu sat up to watch him dry swallow it and they all waited.

It only took a few seconds for a big puff of smoke to engulf him, startling ESPKitty into running upstairs. None of them moved until the smoke cleared, both curious and nervous about the result.

A tiny Karamatsu, probably only about three years old, looked up at them all, and then burst into tears.

* * *

"Oh my fucking God," Osomatsu breathed, watching the Karamatsu from their early childhood bawl in confusion. "Holy shit. Dude, holy shit!"

Choromatsu was taking it about as well but he tried to be the most responsible of the group. "How long is this supposed to last, Jyushimatsu?" he asked, bundling Karamatsu in his now too-big hoodie and lifting him into his lap. Karamatsu calmed down a little once he was in contact with one of his brothers but he still looked awfully disoriented.

Jyushimatsu, eyes wide and a sleeved hand pressed over his mouth, just shook his head.

"Do you think he remembers anything?" Todomatsu asked, shifting closer on his knees. Karamatsu looked away from Choromatsu to his youngest brother, sniffling and mumbling to himself, and Todomatsu gently poked at his cheek until he started to smile.

"Of course he does! He remembers us!" Osomatsu said loudly and surely. "We're his brothers!" Even as he said it, he sidled up next to Todomatsu and wiggled his fingers at the second brother. "Hey, Karamatsu. You remember me, right?"

A moment of tense silence passed before Karamatsu reached up and grabbed one of Osomatsu's fingers. "Nii-chan," he murmured, and Osomatsu nearly passed out from happiness.

Jyushimatsu was the next to crowd around him and reach out. Karamatsu didn't seem overwhelmed at all; in fact, he had stopped crying, and was looking around at the copies of his own face with happiness. "Karamatsu-nii-san, I'm sorry, I didn't know this would happen!" Jyushimatsu said in his best inside-voice, pressing his sleeves to Karamatsu's baby round cheeks and imploring him to understand with his eyes. "We can go to Dr. Dekapan and fix it for you!"

Karamatsu frowned back at him. "Sorry, Jyushimats'," he repeated in a tiny voice. "Jyushima~ts'. Sorry."

"No, you don't be sorry, Karamatsu-nii-san!" Jyushimatsu tried again, but Karamatsu was busy stretching his name as long as he could in his adorable little voice. Osomatsu was still lying on the ground, frothing at the mouth, while the rest of them cooed over their brother.

Ichimatsu shifted just enough that Karamatsu could see him over Choromatsu's shoulder. When their eyes locked, Ichimatsu went still, afraid Karamatsu would burst into tears again at the sight of him. Instead, Karamatsu's eyes absolutely lit up and he scrambled out of Choromatsu's hold. He tripped over the edge of his long hoodie, almost face-planting on the tatami, but was able to keep himself standing long enough to toddle over to Ichimatsu and latch onto him.

"Ichimatsu!" he squealed, and then started babbling something that was mostly unintelligible. All Ichimatsu could do was hug him back, looking down at the top of his brother's head.

"This is too cute." Todomatsu aimed his phone at the two of them, probably taking his most cherished video ever, while Karamatsu's speech slowed to a stop and he looked up at Ichimatsu again, waiting for a reply.

Ichimatsu cleared his throat. "Uh… you're not hurt?" he asked haltingly.

Karamatsu shook his head.

"So, um…." Ichimatsu looked at the ceiling to think. "You really feel this small?"

Shyly, Karamatsu nodded once, and then pressed his face to Ichimatsu's chest.

Ichimatsu began to panic. "N-no, don't cry!" he said, but Karamatsu pulled back again and he was smiling. "Shit, Karamatsu, I thought-"

"I think we should reverse this, sooner rather than later," Choromatsu interrupted. His arms were crossed over his chest, brow furrowed, mouth turned down in a sharp frown, all at odds with the soft, adoring look in his eyes. "Hopefully Karamatsu won't remember it."

"Maybe just a bit longer," Todomatsu said, zooming in on Karamatsu's loving smile and Ichimatsu's smaller one in return.

* * *

 _After:_

"Feelin' okay?" Osomatsu asked his first younger brother, an ice pack pressed against his forehead to maybe chase away some of the cute-induced headache from earlier.

Karamatsu looked sort of hungover but not enough to need ice of his own. "Perfectly fine, brother. Just a little sore. I forgot what it felt like to be that small."

"We all did," Choromatsu said. He had long since given up on pretending to flip through his employment magazine and was reading a book. "I have to admit, you were pretty adorable, Karamatsu-nii-san."

"A reflection of my younger brothers in my eyes," Karamatsu replied, perfectly grandiose, earning an eye-roll in response. He turned toward Ichimatsu, who was sitting in a corner of the room, hugging his knees. When Ichimatsu was caught staring he huffed and faced forward again.

When Ichimatsu looked up again, Karamatsu was sitting in front of him, arms open. "My brother," he began, but was cut off by a swift tap to the sternum. Only when he was wheezing and coughing, hands on his knees, did Ichimatsu hug him momentarily. Everyone else in the room dutifully pretended they didn't see.


End file.
